1. Field of the Invention
The present invention relates to a four-stroke engine.
2. Description of the Related Art
A direct-injection engine is known in which liquid fuel is supplied directly to a combustion chamber so as to improve its output and fuel efficiency.
In the direct-injection engine, fuel is evaporated in a cylinder, and, as a result, the inside of the cylinder is cooled. Therefore, the output of the engine can be improved by increasing the amount of air with which the cylinder is filled. In addition, the temperature of the inside of the cylinder decreases, and therefore knocking can be prevented. Therefore, fuel efficiency can be improved by increasing the compression ratio of an air-fuel mixture.
U.S. Pat. No. 6,053,145 discloses an engine in which liquid fuel is supplied directly to a combustion chamber. In the engine of U.S. Pat. No. 6,053,145, a fuel injector that jets fuel is disposed near intake ports. Two intake ports are provided for each cylinder. The fuel injector is disposed between the two intake ports or is disposed therebelow (i.e., is disposed on a cylinder-body side).